The experiment that revealed the atomic world: Brownian Motion

EDIT: YouTube's compression algorithm seems to have obliterated the smoke jiggles at around 1:00. That combined with an OLED screen makes it look like a black screen! I don't think there's much I can do to be honest so I'm going to leave it up! I didn't get into John Dalton in this video. He noticed that chemical reactions always happened in small whole number ratios of mass. From that he hypothesised the existence of atoms. But Brownian motion is arguably the first direct evidence.

The particle jiggle is actually just floating-point rounding errors in the simulation of the universe.

To be very precise, and to avoid any possible confusion, at 10:19 each syringe doesn't contain 100 million trillion atoms, but 100 million trillion particles of the gas - be they N2 particles, or Ar particles, or CO2 particles, or a mixture of atoms and molecules as in air. This always blew my mind, and the physics behind it is so simple and elegant. Another really great video by Steve.

Well done, but he actually published 5 papers in 1905, his annus mirabilis. These were  1) On the Electrodynamics of Moving. Bodies (Special Relativity) 2) Does the Inertia of a Body Depend on its Energy Content (a study of the consequences of the first reference, where he derived the equivalence of mass and energy i..e. e = mc^2. 3) On the Heuristic Point of View Concerning the Production and Transformation of Light (the photoelectric effect, that ushered in the quantum revolution and his 1921 Nobel Prize) 4) A New Determination of Molecular Dimensions, used to calculate Avogadro's Number and the size of molecules. This paper was in fact a summary of his doctoral dissertation. 5) On the Motion of Small Particles Suspended in Liquids at Rest Required by the Molecular-Kinetic Theory of Heat, which explained Brownian motion as the result of molecular collisions. This insight did in fact lead to a second Nobel Prize in 1926 to Jean Perrin. The five papers are collected together with annotations by John Stachel and a foreword by Roger Penrose, called "Einstein's Miraculous Year"

"Anus mirror balls"?! Steve, you are my FAVORITE science educator, and dumb jokes like this are just icing on the cake.

One piece of intuition missing from the video is that Brownian motion is thermal energy. The more heat, the more motion.

I'm an idiot, I kept hearing "Brownie in motion" at first and I was wondering how Einstein used a Brownie to do science

If you are interested in looking inside of quartz or other crystals, there are many very simple, cheap ways of doing it. We do it in the lab, and there are plenty of papers that actually look at the water within crystals as they tell us a great about about the time at formation of the crystals. We do it for glass inclusions as well. Reach out to a research geologist, and I'm sure someone would be happy to help with your demonstrations, including myself.

It's a good marker for how brilliant Einstein was to say that his 3rd greatest achievement was to prove atoms exist.

1:06 Me watching this outside in bright sunlight and low streaming quality: Oh course, very obvious.

I did a presentation on Brownian Motion during while studying physics in college. Nice to see it get some more attention.

Your style, cadence, and knowledge come together to make videos on complex subjects that are easy to understand and that make learning enjoyable. And I appreciate that you get straight to the point without dawdling about. Thank you for an excellent channel.

Neat stuff! Brownian motion will feature prominently in my next video also. It really is pretty amazing how large the particles can be before the forces average. Really like the vibrating plate demo.

Excellent video Steve! As an MRI radiographer, we study Brownian motion in many of our patients using diffusion weighted imaging. Your explanation here has improved my understanding, thank you!

Thank you for finally explaining this mystery to me. When I was 9 years old, I was asked about Brownian Motion in a physics exam and I had no idea. It was the very first F I got and it's been haunting me for almost 20 years now

Thank you Steve for providing answers to the questions I have always wondered about throughout my life. I love your willingness to experiment to always find a way to explain complex ideas. I and I would imagine plenty of others are grateful for your channel and your passion for science! Much love 🫶🏽

As a Greek, I was especially touched by the "ouzo effect" (and the "Ouzo 12" bottle appearing pouring the liquid)! I had never thought is as a scientific tool - I think I'm going to start experimenting with it, right on!!! 😎😎

It's not the oils in the Ouzo forming an emulsion. The major flavour component of aniseed is methoxybenzene which is soluble in ethanol but poorly soluble in water. When enough water is added, the methoxybenzene comes out of solution as tiny particles in suspension. It's not an emulsion; that would require something to stabilise micelles.

You should do the Millikan oil drop experiment next. I did it 2nd year of college Physics. It's a pretty amazingly simple experiment that determines the mass and charge of an electron with oil mist.

8:22, I was recently telling this to people, hearing from you is also nice. Measuring things that are too small, or too big, or too fast, or too something, is done by matching the observations we made with things we can carefully measure.